Tapping a threaded hole is a common practice in metalworking and manufacturing. It involves cutting internal threads into a pre-drilled hole to enable screwing in a bolt or machine screw. However, tapping a threaded hole can be daunting for those who are new to metalworking or DIY projects. Many people ask how to use a tap to make threaded holes.
First, select the tap size and thread size for your project. A tap is a cutting tool that creates threads and comes in different sizes and shapes. Next, drill a pilot hole of the correct size and depth for the tap. Use a center punch to mark the center of the screw hole, which will be the pilot hole, and keeps the drill bit from wandering.
Once the hole is drilled, begin tapping. Use a tapping tool and tapping fluid to make the tapping process much smoother and prevent damage to the tap or the metal. Begin tapping slowly and carefully, applying pressure while turning the tap in a clockwise rotation.
After cutting a few threads, back the tap off a half rotation counterclockwise to break the chips and avoid cross-threading. When the tap reaches the desired depth, turn it in a full rotation to ensure the threads are complete. Finally, clean the tapped hole of any metal shavings and test the screw threads to ensure they fit correctly.
In our guide, you can learn more about how to tap a hole in the metal and how it differs from a commercial manufacturing process. By the end, you’ll better understand why you need the right drill bit size for the tapping tools you’ll use to make threaded holes. (Read Sloping Driveway Drainage Solutions)
What are the differences between drilling and tapping?
Regarding metalworking, drilling and tapping are two essential processes. Although they share similarities, they differ in their purpose and technique.
Here are some key differences between the drilling process and tapping:
Drilling is creating a hole in a material by removing the material with a drill bit. It is used to create a hole for a bolt or screw to pass through or to create an opening for wires or cables. Tapping, however, are internal threads cutting inside a hole to make threaded holes to create a threaded connection. It is used to create internal threads from the tapping process hole to accept a bolt or machine screw.
Drilling uses a drill bit to remove material from the workpiece. The drill bit is rotated quickly and applied to the workpiece with pressure. Tapping uses a tap to cut threads into the material. The tap is inserted into a pre-drilled hole and rotated to cut threads into the material.
A die tool, in comparison, puts threads on the outside of a piece of metal. The die tool comes in a kit with various sizes of bottoming tap tools.
Drilling requires a drill bit and a drill press or hand drill. The tap drill bit is selected based on the size hole depth of the tapped hole or threaded hole needed. The tapping tool comprises a tap and a tap handle. The bottoming tap is selected based on the size and type of major diameter of thread needed.
Drilling creates a circular hole with a smooth interior surface. The drilled hole is not threaded and cannot accept a bolt or screw without additional steps. Tapped holes are a threaded hole, and the internal thread will accept a bolt or screw without additional steps. The threads a tapping tool creates are stronger than those produced by self-tapping screws.
Preparing to Tap
Before you start tapping, it’s crucial to prepare the hole properly. This will ensure blind holes and the threads are cut cleanly and accurately, and the tap doesn’t break or get stuck in the blind hole itself. (Read Tapcon Drill Bit Size)
Choosing the Right Tap Size
The first step in preparing to tap is to choose the right size tap for the hole. The tap size should match the size of the bolt or screw that will be inserted into the hole.
- If the tap is too small, the threads won’t be strong enough to hold the bolt securely.
- If the tap is too large, the threads may not fit properly and could strip the hole.
Drilling the Hole
Once you have chosen the right tap size, you must drill the hole to the correct size. The threaded hole drilled out should be slightly smaller than the bolt’s diameter, allowing room for the threads to be cut. Use a drill-cutting tool the same size as the tap or slightly smaller. If the to-be-threaded holes are too small, the tap won’t fit properly and could break. If the soon-to-be tapped holes are too large, the threads won’t be strong enough to hold the bolt securely in the tapped holes.
Before drilling the hole, mark the center of the hole with a center punch to ensure the drill bit doesn’t wander. Use a pilot hole if necessary to help guide the drill bit cutting tool into a smooth hole. When drilling the hole, ensure the drill bit (end mill) is perpendicular to the surface or smooth edge of a blind hole being drilled. If the hole is drilled at an angle, the threads will be crooked, and the bolt won’t fit properly.
If the hole is drilled into an angled surface, it’s important to ensure it is drilled straight. Use a drill press or a guide to ensure the hole is drilled at the correct angle. Once the hole is drilled, use a chamfer tool to remove any burrs or rough edges from the bottom tap and hole. This will help the taper tap start more quickly and prevent the bottom tap from breaking inside the tapped hole.
Tapping the Hole
Regarding tapping a hole, you must remember a few things to ensure a smooth and successful process. In this section, we’ll cover the basics of using the taper tap, the difference between taper taps and plug taps, and creating your own threads.
Using the Tap
You’ll need a tap handle and a correct size tap drill to use the tap. Start by drilling a hole in the metal at the right size for the tap. Next, insert the tap into the tap handle and place it in the hole. Ensure the tap is in the correct position and begin rotating it clockwise. Keep turning the tap handle until you’ve created enough threads for the screw to fit in.
Remember to avoid putting too much pressure on the tap handle and allow the tap to thread the screw hole on its own.
Taper Taps vs. Plug Taps
There are two types of taps: taper taps and plug taps. A taper tap has a more gradual thread and is used to start new holes. Plug taps, however, have a more aggressive thread and are used to create threads and finish threads to begin the threading process. When using a taper tap, only thread a few threads before switching to a plug tap.
When creating threads, it’s vital to avoid cross-threading. Cross-threading occurs when the screw is inserted at the wrong angle, damaging the threads. To prevent this, ensure the tap is in the correct position and rotate it clockwise. Use tapping fluid or other suitable lubricant to lubricate the tap, reduce the amount of metal shavings, and make the hole easier to tap.
After a few rotations, back the tap out to remove the shavings and continue tapping until you have enough threads for the screw to fit in blind holes. In conclusion, tapping a specific hole requires the correct size tap drill, handle, and tap. Remember to use tapping fluid and avoid cross-threading. Following these steps, you can create smooth tapped threaded holes anywhere, with even consistent threads. (Learn How To String A Weed Eater With Two Holes)
Finishing the Job
Congratulations, you have successfully tapped a threaded hole! However, your job is not yet complete. You must take a few more steps to ensure the threaded hole is clean, functional, and ready to use.
After tapping the hole, cleaning up any debris or metal shavings left behind is essential. This will help prevent any damage to the threads and ensure the bolt or screw can be inserted smoothly. You can clean up the tapped hole using a few different methods:
- Blow out the hole with compressed air.
- Use a brush or rag to wipe away any debris.
- Use a tap wrench or pliers to remove broken taps or other obstructions.
Testing the Threads
Before inserting a bolt or screw, testing the threads to ensure they are functional is essential. You can do this by inserting a bolt or screw into the threaded hole and turning it clockwise. The threads are functional if the bolt or screw turns quickly and smoothly. If the bolt or screw does not turn quickly or feels rough, the threads may be damaged or improperly formed.
If you encounter any issues with the threads, you must re-tap the screw hole or use a different-sized tap. Using the correct screw thread, size and type for your application is also essential. Machine screws and bolts typically have standard thread sizes, while custom or specialized applications may require non-standard thread sizes. (Learn How To Fill Chipmunk Holes)
- When tapping hard materials, using a cutting fluid to lubricate the tap and reduce friction may be helpful.
- When using a hand tap, turn the tap a full rotation clockwise and then a half rotation counterclockwise to break chips and prevent the tap from breaking.
- If a tap breaks off in the new hole, it may be necessary to use a special tool to remove the broken tap.
- Always be careful when tapping holes, as the hand tap can break, or the threads can be damaged if not done correctly.
By following these steps and using the proper techniques, you can create functional and reliable internal and external threads that enable screwing in threaded components. Whether you use a forming tap or a cutting tap, take your time and be patient when tapping holes to ensure a successful outcome.